The third cause of death of the Japanese people is pneumonia, and 90% or more of pneumonia of elderly people is said to be aspiration pneumonia. When elderly people suffer from pneumonia, they may be hospitalized for a longer time, rapidly deteriorate in physical strength and the like, and have a risk of becoming frail (a state of being declined in muscular strength and vitality due to advanced age), suffering from sarcopenia (a phenomenon of age-related muscular decline), and the like. For the extension of healthy life expectancy and the restraint of medical costs, attention is being paid to the mechanism of a living body during swallowing and to behavior of an alimentary bolus during swallowing.
Swallowing is a reflex motion to send food (including drinks) taken into the oral cavity, to the stomach through the pharynx and the esophagus. During swallowing, muscles of the oral cavity, the pharynx, the larynx, and the esophagus act in a set order within a short time, and achieve a complicated motion.
As a technique to simulate behavior of an alimentary bolus during swallowing, there has heretofore been disclosed a swallowing dynamic state simulator using a computer (PATENT LITERATURES 1 and 2). PATENT LITERATURE 1 discloses a swallowing simulation device which includes oral cavity modeling, an organ properties setting unit, an organ motion setting unit, a food physical properties setting unit, a motion unit, a physical properties deciding unit, and a control unit.
A swallowing dynamic state and alimentary bolus behavior can be simulated on a computer. It is possible to extract an alimentary bolus downward flow velocity during swallowing, acceleration, shear velocity, shear stress, viscosity of food, force on living body organs, energy, and others. Not only data at a given time and position but also changes in physical quantity during a swallowing operation can be extracted, and then visualized and quantified.
PATENT LITERATURE 2 discloses a swallowing simulation device which includes a head and neck modeling unit, an organ motion setting unit, an oral ingestion material physical properties setting unit, an input unit to input a false oral ingestion material into the oral cavity; a motion analysis unit, a physical properties deciding unit, and a control unit.
A swallowing dynamic state and alimentary bolus behavior can be simulated on a computer. It is possible to extract an alimentary bolus downward flow velocity during swallowing, acceleration, shear velocity, shear stress, viscosity of food, force on living body organs, energy, and others. Not only data at a given time and position but also changes with time in physical quantity during swallowing operation can be extracted, and then visualized and quantified.
Another technique to simulate behavior of an alimentary bolus during swallowing can measure fall velocity, fall aspect, and a fall path of a false food by use of a full-scale oropharyngeal model manufactured by a powder deposition method. There is disclosed a method to compute a velocity on the basis of a contrast photograph of swallowing (refer to NONPATENT LITERATURE 1).
Furthermore, a measurement method of physical quantity directed to micro liquid droplets is disclosed as measurement that considers water repellency (or wettability) of food and a wall surface (PATENT LITERATURES 3 and 4). PATENT LITERATURE 3 discloses an evaluation device for wettability including a light source which illuminates a specimen from above, an upper surface measurement camera which sends upper video data resulting from photography of the specimen from above to a personal computer main unit, a light source which illuminates the specimen from the side, a camera which sends side video data resulting from sidewise photography to the personal computer main unit, a specimen stage which adjusts droplet hitting positions on a liquid specimen or a solid specimen, and the personal computer main unit which calculates the video data. This device can capture a liquid droplet from the side and then measure and compute a contact angle, a liquid diameter, a liquid height, and a liquid amount, and can also capture the liquid droplet from its upper surface photographed simultaneously with its side surface and then evaluate the circularity of the liquid droplet and the water repellency dependent on a wet area.
PATENT LITERATURE 4 discloses a measurement method of liquid droplet moving behavior to measure, with a camera, the acceleration of one point on a moving direction side, between two points on both sides of the intersection of a liquid droplet outer periphery and a solid substance surface seen from the side of the moving direction when the liquid droplet moves on a fixed surface. A dynamic contact angle based on a dynamic falling method can be measured; and movement distance, velocity, acceleration, and the upper surface can be observed, so that shear velocity and shear stress can be measured from a velocity distribution of flux inside the liquid droplet.